This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Rotating frame relaxation MRI contrast, T1rho and T2rho, are thought to provide sensitive indicators of tissue changes in hyperacute stroke. In this work, we are investigating the changes in T1rho and T2rho MRI of infarcting brain, and have recently shown that the changes in hyperacute stroke reflect an increase in the free water pool size, decreased tumbling of the water molecules associated with macromolecules, and increased water exchange between free and macromolecular sites. These findings are consistent with vasogenic edema, destructive processes and tissue acidification. This research is providing new insights into the physico-chemical processes occurring in brain ischemia